This invention relates generally to cardiac rhythm management devices and methods, and more particularly to an implantable device, such as a cardioverter-defibrillator, and method for treating atrial tachyarrhythmias.
Atrial tachyarrhythmias are quite common, and are seen even in patients who are not acutely ill. One such atrial tachyarrhythmia, atrial fibrillation, does not usually pose an immediate threat to the patient""s life, but prolonged atrial fibrillation can compromise patient hemodynamics. Inadequate blood flow due to atrial fibrillation may lead to blood clots, which increase the risk of strokes. Other symptoms may include palpitations of the heart, dizziness, or loss of consciousness.
One method of treating atrial fibrillation is to deliver a countershock to terminate the arrhythmia. For example, the countershock may be applied via an external or implantable defibrillator. However, this method of treating atrial fibrillation risks causing ventricular tachyarrhythmias, including life-threatening ventricular fibrillation.
One method of reducing the risk of ventricular fibrillation is by synchronizing the delivery of a countershock to an electrical ventricular activation (R-wave) of the heart. There is, however, a need in the art to further reduce the risk of inducing ventricular tachyarrhythmias, such as life-threatening ventricular fibrillation, during the countershock treatment of comparatively less exigent atrial tachyarrhythmias.
The present invention provides a method of applying anti-tachyarrhythmia therapy, such as a countershock, to the heart. From the atrium of the heart, atrial activity needing anti-tachyarrhythmia therapy is detected. Ventricular activity is monitored for an indication of abnormal susceptibility to ventricular tachyarrhythmia. Anti-tachyarrhythmia therapy is delivered to the atrium in response to the detected atrial tachyarrhythmia activity. But the atrial tachyarrhythmia therapy is delayed for a first time delay if the indication of abnormal susceptibility to ventricular tachyarrhythmia is detected.
The present invention also provides an device, such as an implantable cardioverter-defibrillator, for delivering anti-tachyarrhythmia therapy to the heart. An atrial receiver receives an atrial heart activity signal from an atrium of the heart. A ventricular receiver receives a ventricular heart activity signal from the ventricle of the heart. A controller controls the delivery of the anti-tachyarrhythmia therapy to the atrium in response to the atrial heart activity signal indicating a need for the anti-tachyarrhythmia therapy. The controller includes a first timer for delaying the delivery, by a first time delay, of the anti-tachyarrhythmia therapy to the atrium in response to the ventricular heart activity signal indicating abnormal susceptibility to a ventricular tachyarrhythmia.
In one embodiment, the countershock or other anti-tachyarrhythmia therapy is synchronized to or delayed from the R-wave. In another embodiment, following the indication of abnormal susceptibility to a ventricular tachyarrhythmia, the first timer is reset and the value of the first time delay is adjusted according to the particular type of indication of abnormal susceptibility to a ventricular tachyarrhythmia. The value of the first time delay can be programmed depending on the patient""s vulnerability to ventricular tachyarrhythmia. The delay can be programmed to exceed approximately one second or approximately several hours. In one embodiment, the first timer is reset and the value of the first time delay is adjusted subsequent to delivery of an atrial countershock.
The present invention delays delivery of atrial anti-tachyarrhythmia therapy when an indication of abnormal susceptibility to a ventricular tachyarrhythmia is present. As a result, the present invention reduces the risk of reinducing ventricular tachyarrhythmias, such as life-threatening ventricular fibrillation, which can be caused by the delivery of anti-tachyarrhythmia therapy to the atrium.